Multi-gas flow sensor with gas specific calibration capability

ABSTRACT

A multi-gas/gas-mixture or liquid flow sensor apparatus utilizing a specific media calibration capability. The flow sensor can be coupled with an Application Specific Integrated Circuit (ASIC) that incorporates a signal conditioner and a memory module. The signal conditioner provides a high order calibration and signal processing of flow signals from the sensor to a processed signal output representative of the flow. The processed signal output can be stored in the memory module. A correction factor can be calculated and stored in the memory module in response to the stored values of the processed signal output, which tends to linearize the relationship between the flow rate and the processed signal output of a measuring system. The correction factor and/or the processed signal output provided by the signal conditioner can be utilized by the measuring system.

This application is a continuation of U.S. patent application Ser. No.12/166,047, filed Jul. 1, 2008, and entitled “Multi-Gas Flow Sensor WithGas Specific Calibration Capability”, which is incorporated herein byreference.

TECHNICAL FIELD

Embodiments are generally related to sensor methods and systems.Embodiments are also related to combi sensors for measuring multiplemeasurands. Embodiments are additionally related to multi-gas flowsensors.

BACKGROUND OF THE INVENTION

Flow sensors are utilized in a variety of fluid-sensing applications fordetecting the movement of fluids, which may be in gaseous (e.g., air) orliquid form. A gas mass flow sensor is one example of a flow sensor.Examples of gas sensing applications utilizing mass gas flow sensorsinclude anesthesia gas mixers employed in medical applications, high-endwelding equipment utilized in industrial applications, and gaschromatography detectors and controllers implemented in instrumentationapplications. Typical sensor instrumentation utilized in suchapplications includes, for example, one or more simultaneous measurandto make calculations for sensor measurement. This is currently achievedby either using multiple sensors with different addresses or a singlesensor with a complex system level calibration selection that utilizes aconditioning microcontroller or a PLC (Programmable Logic Controller).

Flow sensors inherently produce a nonlinear output signal in response togaseous or liquid flow through the sensor. Such nonlinear output signalsare dependent upon many factors, such as temperature coefficients ofresistance with respect to the utilized sensing element, thermaltransfer characteristics of the media being measured and the media ofthe transducer, and the mechanical dimensions of a flow path.

Signal conditioning circuits are often utilized as an interface in asignal conditioning unit to convert a basic flow signal received from adata source into a more usable output signal. Signal conditioningcircuits can be utilized in association with flow sensors to receive anon-linear flow signal and convert the basic flow signal into an outputvoltage utilized by a control system. Application Specific IntegratedCircuit (ASIC) components have been developed for conditioning sensorinput signals and such ASIC's offer a wide variety of programmingoptions that can be specifically tailored to match the characteristicsof the particular sensor technology.

The majority of prior art sensing applications possess limited sensingand signal conditioning capabilities. Such sensing applications utilizemultiple sensors, complex calibration routines and expensivemicro-controllers/PLCs to condition basic flow signals from the sensor,regardless of the quantity being measured by the sensor. This approachresults in a complex system calibration, which leads to an increase inprocessing time and often produces inaccurate results. Additionally, theinstallation costs for packaging individual sensors for such applicationincreases, which further enlarges the size of the final sensor package.

Based on the foregoing it is believed that a need exists for an improvedmulti-gas flow sensor utilizing a combi sensor with gas calibrationcapability as described in greater detail herein. A need also exists foran improved signal conditioning circuit that is capable of conditioningthe basic flow signal output from different types of sensors.

BRIEF SUMMARY

The following summary is provided to facilitate an understanding of someof the innovative features unique to the embodiments disclosed and isnot intended to be a full description. A full appreciation of thevarious aspects of the embodiments can be gained by taking the entirespecification, claims, drawings, and abstract as a whole.

It is, therefore, one aspect of the present invention to provide for animproved sensor method and apparatus.

It is another aspect of the present invention to provide for an improvedcombi sensor apparatus for measuring multiple measurands in a commonpackage.

It is a further aspect of the present invention to provide for animproved multi-gas flow sensor utilizing a combi sensor with gasspecific calibration capability.

The aforementioned aspects and other objectives and advantages can nowbe achieved as described herein. A multi-gas flow sensor apparatus andmethod is disclosed herein, which includes the use of a combi sensorwith gas calibration capabilities. The combi sensor can be coupled witha conditioning microcontroller that incorporates a signal conditionerand a memory module. The signal conditioner provides a high ordercalibration and signal processing of flow signals from the combi sensorto a processed signal output representative of the flow. The processedsignal output can be stored in the memory module. A correction factorcan be calculated and stored in the memory module in response to thestored values of the processed signal output, which tend to linearizethe relationship between the flow rate and the processed signal outputof a measuring system. The correction factor and/or the processed signaloutput provided by the signal conditioner can be utilized by themeasuring system.

The combi sensor includes a number of varying types of sensors thatprovide multiple sensing measurands for sensing operations. The ASICmemory and the signal conditioner can be connected to a number ofvarying types of sensors. The ASIC stores calibration data and sensorrelated information utilizing the memory for each of the connectedmeasurand transducers.

Additional correction factors to the processed signal outputs can beutilized depending on the measuring system, which require changes whenthe gas type also changes. Important measurands for accuratelycalculating the mass flow of different gases is: which gas is in theflow channel, the absolute temperature and the barometric pressure.Humidity can also be processed and may be used in the furthercalculations of the gas mass flow. The combi sensor output is providedto a conditioning microcontroller where the information can be processedinto an accurate output signal for specific gas output. The multi-gasflow sensor with gas specific calibration disclosed herein can thereforeprovide a calibrated coarsely conditioned signal output for variousknown gases.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the embodiments and, together with the detaileddescription, serve to explain the embodiments disclosed herein.

FIG. 1 illustrates a block diagram of a multi-gas flow sensor, which canbe utilized for providing a calibrated and accurately conditionedoutput, in accordance with a preferred embodiment; and

FIG. 2 illustrates a flow chart of operations illustrating operationalsteps of a method for providing high order calibration and signalprocessing of the multi-gas flow sensor output signal, in accordancewith a preferred embodiment.

DETAILED DESCRIPTION

The particular values and configurations discussed in these non-limitingexamples can be varied and are cited merely to illustrate at least oneembodiment and are not intended to limit the scope thereof.

FIG. 1 illustrates a block diagram 100 of a flow sensor apparatus 110,which can be utilized for providing a calibrated gas/gas-mixture orliquid specific conditioned output, in accordance with a preferredembodiment. The flow sensor apparatus 110 is connected to one or moreflow sensors within sensed parameters 125 and contains sensor processingability. The flow sensor apparatus 110 is also connected to the end-userdevice 160. The flow sensor apparatus 110, in one embodiment, can beimplemented as an Application Specific Integrated Circuit (ASIC) “combisensor” apparatus 120 and a conditioning microcontroller 130 comprisedof a signal conditioner 140 and non-volatile memory 150. It is importantto note, however, that a combi sensor represents merely one possibleimplementation. For purposes of discussion and of providing anillustrative example, the disclosed embodiments provide an example of acombination sensor. Note that the term “combi sensor” as utilized hereingenerally refers to a combination sensor that often incorporates one ormore sensor transducers, such as, for example, mass flow, pressure,temperature and humidity.

The flow sensor apparatus 120 can be configured to include a number ofvarying types of sensors 125 processed by the combi sensor ASIC 120within functional compensation blocks for each measurand 122, 124, 126and 128 that can provide compensated outputs for the multiple sensingmeasurands for sensing operations. The conditioning microcontroller 130further includes a signal conditioner 140 with associated memory 150.The combi sensor ASIC 120 senses environmental parameters 125 such asairflow, pressure, temperature and humidity in order to providecompensated measurand signals 132, which are each in the presence of thenon-linear response to the gas/gas mixture or liquid mass flow throughthe combi sensor 125. Such an output signal is dependent upon manyfactors such as temperature coefficients, thermal transfercharacteristics of the media being measured and the media of thetransducer, and the mechanical dimensions of the flow path. The basicflow signals can be conditioned and calibrated by the signal conditioner140 associated with the ASIC 130.

The compensated measurand signals generally correspond to the parameters125 sensed by the combi sensor 120. The conditioning microcontroller 130feeds-back coefficients to the combi sensor 120 based on informationabout the gas/gas-mixture or liquid being sensed. The signal conditioner140 uses the conditioned measurands from the combi sensor 120 and usescalculations to provide a processed output signal 160. Coefficients togenerate the processed output signal 160 can also be stored in thememory 150. Information pertaining to the gas/gas-mixture or liquid flowis generally provided by an end-user device. A correction factor can becalculated and stored in the memory 150 based on the stored values ofthe processed signal output 160, which will tend to linearize therelationship between the flow rate and the processed signal output 160of a measuring system.

The memory 150 comprises a rewritable nonvolatile memory, an EEPROM(Electrically Erasable Programmable Read Only Memory) or flash EPROM;however, other rewritable ROMs may also be used. The conditioningmicrocontroller 130 can be utilized to store and provide flow-specificcoefficients 134 and pertinent sensor related information to one or moreof the sensors 122, 124, 126 and 128 utilizing the EEPROM 150. Ingeneral, conditioning microcontroller 130 can be implemented as an ASICthat is designed essentially from “scratch” for a specific application.ASIC IC's are specially designed chips that provide unique functions.ASIC IC's can replace general-purpose commercial microcontroller IC'sand integrate several functions or logic control blocks into one singlechip, lowering manufacturing cost and simplifying circuit board design.It can be appreciated that other types of ASIC devices may also beutilized to implement signal-conditioning ASIC 130, depending upondesign considerations.

The memory 150 stores flow-specific information 164 provided from theend-user device 160 by an end-user to perform particular tasks. End-userdevice 160 can include, for example, a microprocessor utilized by theend-user to analyze, store, and otherwise utilize the data from the flowsensor apparatus. The microprocessor may be dedicated for that purpose;more typically the microprocessor will be part of a larger measuringsystem that uses the analyzed data for some other purpose, (e.g., apatient monitor used for monitoring the breathing, temperature, andheart rate of a hospital patient). The flow-specific information 164 orthe processed signal output 162 can be utilized depending on themeasuring systems, which require changes when gas/gas-mixture or liquidtype changes.

FIG. 2 illustrates a high-level flow chart of operations illustratingoperational steps of a method 200 for providing high order calibrationand signal processing of the multi-gas or liquid flow sensor outputsignal in accordance with a preferred embodiment. Note that in FIGS.1-2, identical or similar blocks are generally indicated by identicalreference numerals. The combi sensor 120 can be configured, as depictedat block 210 based on gas/gas-mixture or liquid flow information 164through the measurand specific coefficients 134. The varying types ofsensors in environmental parameters 125 input into the combi sensor ASIC120 with compensation modules 122, 124, 126 and 128 can include one ormore of the following types of sensors: a flow sensing element, apressure sensing element, a temperature sensing element and/or ahumidity sensing element.

The present invention is particularly useful where at least one of thesensor-transducers associated with the combi sensor 120 is sensingparameter(s) that result(s) in a highly non-linear output, such as asensor transducer that is sensing the gas/gas-mixture or liquid flow.The combi sensor ASIC utilizes measurand coefficients 134 provided fromthe conditioning microcontroller 130. Thereafter, the combi sensor 120can be electrically connected to a conditioning microcontroller 130 thatincludes a signal conditioner 140 and memory 150, as illustrated atblock 220. Next, the basic flow signals and environmental parameters 132can be obtained from sensed parameter(s) 125 utilizing the combi sensor120, as depicted at block 230 and stored in memory 240.

Correction factors can be calculated 250 and stored in memory 260 basedon the compensated parameter signals 132 which are stored in the memoryand further processed and calibrated by the conditioning microcontroller130. The flow output signal 162 is generated using all of thecompensated measurand signals and correction factors, as illustrated atblock 270. The processed flow output signal is provided to the end-userdevice by the conditioning microcontroller 280. It is believed that byutilizing the multi-gas/gas-mixture or liquid flow sensor apparatus 110as described herein, the sensed parameters can be conditioned to providea fine and processed output utilizing a single package that is verysmall in size and cost effective.

It will be appreciated that variations of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A mass flow sensor apparatus for sensing a mass flow rate of a fluidtraveling down a flow channel, wherein the fluid is a known fluid typeof two or more fluid types each having different fluid characteristics,comprising: a mass flow sensor for sensing the mass flow rate of thefluid traveling down the flow channel, the mass flow sensor providing amass flow rate signal; a non-volatile memory storing: a first set ofcoefficients that correspond to a first fluid type of the two or morefluid types; a second set of coefficients that correspond to a secondfluid type of the two or more fluid types, wherein the first set ofcoefficients are different from the second set of coefficients; and acontroller that: reads the first set of coefficients from thenon-volatile memory and compensates the mass flow rate signal using thefirst set of coefficients when the first fluid type is traveling downthe flow channel; and reads the second set of coefficients from thenon-volatile memory and compensates the mass flow rate signal using thesecond set of coefficients when the second fluid type is traveling downthe flow channel.
 2. The mass flow sensor apparatus of claim 1, whereinthe mass flow rate signal is at least partially compensated before thecontroller compensates for fluid type via the first set of coefficientsor the second set of coefficients.
 3. The mass flow sensor apparatus ofclaim 1, wherein the mass flow rate signal is at least partiallycompensated after the controller compensates for fluid type via thefirst set of coefficients or the second set of coefficients.
 4. The massflow sensor apparatus of claim 1, wherein the mass flow sensor and thenon-volatile memory are situated in a common sensor package.
 5. The massflow sensor apparatus of claim 4, wherein the controller is situated inthe common sensor package.
 6. The mass flow sensor apparatus of claim 4,wherein the controller is part of an End-User device separate from thecommon sensor package.
 7. The mass flow sensor apparatus of claim 1,further comprising a plurality of other sensors, each of the pluralityof other sensors sensing a different property of the fluid travelingdown the flow channel.
 8. The mass flow sensor apparatus of claim 7,wherein at least selected sensors of the plurality of other sensors havea corresponding first set of coefficients and a corresponding second setof coefficients stored in the non-volatile memory.
 9. A sensor apparatusfor sensing a property of a fluid traveling down a flow channel, whereinthe fluid is a known fluid type of two or more fluid types each havingdifferent fluid characteristics, the sensor apparatus comprising: asensor for sensing the property of the fluid traveling down the flowchannel; a non-volatile memory storing: a first set of coefficients thatcorrespond to a first fluid type of the two or more fluid types; asecond set of coefficients that correspond to a second fluid type of thetwo or more fluid types, wherein the first set of coefficients aredifferent from the second set of coefficients; and the sensor and thenon-volatile memory are situated in a common sensor package.
 10. Thesensor apparatus of claim 9, wherein said sensor provides a signalrelated to the property of the fluid traveling down the flow channel,and wherein: said first set of coefficients, once read from thenon-volatile memory, are used to compensate the signal when the firstfluid type is traveling down the flow channel; and said second set ofcoefficients, once read from the non-volatile memory, are used tocompensate the signal when the second fluid type is traveling down theflow channel.
 11. The sensor apparatus of claim 10 further comprising acontroller that: reads the first set of coefficients from thenon-volatile memory and compensates the signal using the first set ofcoefficients when the first fluid type is traveling down the flowchannel; and reads the second set of coefficients from the non-volatilememory and compensates the signal using the second set of coefficientswhen the second fluid type is traveling down the flow channel.
 12. Thesensor apparatus of claim 11, wherein the signal is at least partiallycompensated before the controller compensates the signal for fluid typevia the first set of coefficients or the second set of coefficients. 13.The sensor apparatus of claim 11, wherein the signal is at leastpartially compensated after the controller compensates the signal forfluid type via the first set of coefficients or the second set ofcoefficients.
 14. The sensor apparatus of claim 11, wherein thecontroller is situated in the common sensor package.
 15. The sensorapparatus of claim 11, wherein the controller is part of an End-Userdevice situated outside of the common sensor package.
 16. The sensorapparatus of claim 9 further comprising a plurality of sensors, each ofthe plurality of sensors sensing a different property of the fluidtraveling down the flow channel.
 17. The sensor apparatus of claim 16,wherein at least selected sensors of the plurality of sensors have acorresponding first set of coefficients and a corresponding second setof coefficients stored in the non-volatile memory.
 18. A method forproviding a measure related to a property of a fluid traveling down aflow channel, wherein the fluid is a known fluid type of two or morefluid types each having different fluid characteristics, the methodcomprising: sensing the property of the fluid traveling down the flowchannel using a sensor, and providing a signal related to the propertyof the fluid traveling down the flow channel; compensating the signalfor fluid type by: identifying if a first fluid type is traveling downthe flow channel or if a second fluid type is traveling down the flowchannel; if the first fluid type is traveling down the flow channel,reading a first set of coefficients from a non-volatile memory, andcompensating the signal using the first set of coefficients; and if thesecond fluid type is traveling down the flow channel, reading a secondset of coefficients from the non-volatile memory, and compensating thesignal using the second set of coefficients; and providing a compensatedoutput signal that is related to the property of the fluid travelingdown the flow channel.
 19. The method of claim 18, wherein the sensorand the non-volatile memory are situated in a common sensor package. 20.The method of claim 18, wherein the identifying step identifies if afirst fluid type is traveling down the flow channel or if a second fluidtype is traveling down the flow channel by receiving a fluid type inputsignal.